A bilateral polishing or lapping process for semiconductor wafers, has been described in U.S. Pat. No. 3,691,694 and in an article published in the IBM Technical Disclosure Bulletin, Vol. 15, No. 6, of November 1972, pages 1760-1761 (authors: F. E. Goetz and J. R. Hause). In these publications, carrier disks made of a metal such as steel plate or consisting entirely of plastic material are disclosed.
Although metal carrier disks provide long service life, in the course of the machining operation especially in the case of semiconductor wafers that are often brittle and sensitive to mechanical stresses, the edges of the wafer are damaged and thus a large portion of the machined wafers cannot be used. The edge damage does not appear in wafers machined using carrier disks made of plastic material. However, the service life of plastic carrier disks is short. The external periphery of plastic carrier disks cannot withstand the mechanical stresses caused by a drive unit comprising planetary gearing.
The object of the present invention is to provide a process that allows bilateral abrasive machining such as lapping or polishing of wafer-like workpieces with low mechanical stressing of the edge of the workpiece together with a long service life of the carrier disks.